1. Field of the Invention
The present invention relates to a fill system for a packaging machine. Specifically, the present invention relates to a hygienic fill system for a linear form, fill and seal packaging machine.
2. Description of the Related Art
Packaging machines are known that integrate into a single unit the various components necessary to form a container, fill the container with a liquid product, and seal the container. Such packaging machines typically feed carton blanks into the machine, seal the bottoms of the cartons, fill the cartons with a product dispensed from a product storage tank, seal the tops of the cartons, and off-load the filled cartons for shipping.
A popular type of carton is an Extended Shelf Life ("ESL") carton due to the added value such a carton presents to a retailer. For example, pasteurized milk processed and packaged under typical conditions has a shelf life at four degrees Celsius of seven to fourteen days while the same milk processed and packaged under ESL conditions has a shelf life of fourteen to thirty days. Under ESL conditions, juice may have a shelf life of forty to one-hundred twenty days, liquid eggs sixty to ninety days, and egg nog forty-five to sixty days. Thus, ESL packaging greatly enhances a product since it extends the time period that the particular product may be offered for sale to the consuming public. An ESL carton is the final component of an ESL system which entails ESL processing and ESL filling. In order to have ESL filling, the filling system should be kept sterile in order to prevent contamination of the product or carton during filling on a form, fill and seal package machine.
As the product is dispensed from the product tank during the packaging process, compensation must be made for the displacement of the product in the product tank. Thus, it is desirable to vent the product tank in order to compensate for the displacement of the product. Where the product is a liquid foodstuff, it may be necessary to maintain a sterile environment in the tank. Therefore, the tank cannot be vented to the open atmosphere.
One solution to the problem of venting the product tank while maintaining a sterile environment in the product tank is set forth in U.S. Pat. No. 5,009,339 to Hanerus et al. The '339 patent illustrates an apparatus for venting a plant for filing containers. The apparatus includes two control valves disposed at an outlet from the product tank and a vacuum pipe and pump assembly provided along an upper edge of the product tank.
Although a product tank can be vented in this manner at conventional operating speeds, new problems are presented as packaging machines are designed for ever-increasing through put capacities. Specifically, cartons are typically lifted into a sterile filling environment. At high operating speeds, sterile air that is displaced by lifting the cartons to be filled into the filling environment presents a problem that is not dealt with in the prior art, namely the problem of venting both the filling environment and the product tank. Additionally, vents disposed exterior to the tank present problems with clean in place (CIP) systems since the vent must necessarily be cleaned in a separate, manual cleaning step.
As a result, Franke et al. disclose in U.S. Pat. No. 5,533,550 an apparatus for internally venting a product tank in a packaging machine which solves the problems of the '339 patent. The Franke et al. patent is owned by the assignee of the present application.
In addition, a filtered clean air supply is necessary for the product tank. Such a filtered clean air supply is used to supply clean air for breathing in the tank and cleaning the box during production and also to keep the level low in the product tank during cleaning. A need exists for such a filtered clean air supply at the top of the product tank.